JPS63268563A - Device for matrix-binding printed wiring circuit board by solder - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial Application Field The present invention relates to an apparatus for soldering electrical and electronic components onto a circuit board as a substrate, and more particularly, to an apparatus for soldering electrical and electronic components onto a printed circuit board or similar board. and an improved apparatus for mass soldering electronic components by the leads of those components.

(o) Prior Art Various soldering systems are well known in the art for mass soldering electrical and electronic components onto printed wiring circuit boards by means of the leads of those components. One method for mass soldering components is dip soldering. According to this method, the entire surface of a circuit board having printed wiring is brought into engagement with the surface of a bath of molten solder for a period of time with leads protruding through certain holes from the component and then Another method for mass soldering components onto a removed circuit board is wave soldering. A typical conventional wave soldering system generally includes a container adapted to hold a source of molten solder and a reservoir partially immersed in the molten solder. The reservoir has an inlet orifice below the surface of the molten solder and an elongated horizontal nozzle or slot above the surface of the solder. A positive displacement pump is submerged into the solder and is adapted to force the molten solder into the reservoir's intake orifice, where the molten solder then flows upwardly into the reservoir and exits through the horizontal nozzle. This creates a smoothly rounded standing wave of molten solder above the nozzle. Other methods of mass soldering electrical and electronic components onto printed circuit boards are well known in the art and include:
It also includes cascade soldering, jet soldering and dog soldering. flat nosock (f
So-called "leadless" components, such as latpacks), also involve securing said component to the bottom of a circuit board, for example by means of a fixture or by means of adhesive, and then bonding the bottom of the board and said component with molten solder. It can be mass soldered to a circuit board by engaging with. Although known mass soldering systems are economical to manufacture and therefore have substantial commercial use in the electronics industry, they often result in excessive solder being deposited on the circuits, connections and leads of the board. It's becoming a problem.

If excess solder adheres, it will cause short pieces, icicles and/or
Bridges may form and increase the weight of the board due to solder consumption and finish. Furthermore, the formation of solder strips, icicles, and bridges has become increasingly problematic as the electronic industry is currently trending towards relatively high densities of electronic assemblies.

Various methods have been devised in the past to solve the problem of forming solder strips, icicles and bridges.

For example, for wave soldering, one method that has become virtually universally adopted in the industry is to solder the solder waves in such a way as to increase the exit angle between the solder wave and the circuit board being soldered. It involves tilting the path of the circuit board through from the horizontal. Various waveforms have also been devised to further increase the exit angle and/or change the point of exit of the circuit board from the wave. Although increasing the exit angle of the plate from the wave has been found to substantially reduce the formation of solder chips, bridges and/or icicles,
Doing this eliminates the formation of solder stubs, bridges, and icicles, especially when soldering components of relatively high density electronic assemblies and/or relatively long lengths of lead wire. I don't. Additionally, tilting the conveyor to increase the exit angle increases the height of the soldering system and complicates the feed system between the assembly operation point and the cleaning operation point, which typically employs a horizontal conveyor. become. Changing the reservoir and nozzle to increase the exit angle and/or change the point of exit of the circuit board from the wave complicates the waveform and control system.

Another system that is substantially commercially acceptable for reducing the formation of solder patches, icicles, and bridges is the intimate mixing of the Walker et al. patent oil. Although such systems have been found to substantially reduce the formation of solder stubs, bridges and/or icicles, they are particularly useful for circuit boards with relatively high density electronic assemblies and/or When soldering components with long IJ+ conductors, the formation of solder stubs, bridges, and icicles is not inevitable.

(8) Problems to be Solved by the Invention Therefore, it is a main object of the present invention to provide a mass soldering apparatus that overcomes the problems of the prior art as described above.

It is also an object of the present invention to provide an improved mass soldering apparatus that alleviates the problem of solder stubs, icicles and/or bridges forming.

A more specific object is to provide an apparatus for mass soldering relatively high density circuit board assemblies.

11F of the margin specification below (no change in content) (d) Means for solving the problem The present invention provides a circuit board having a lead wire that penetrates a hole in the circuit board and protrudes downward. An apparatus for mass joining electrical and electronic components incorporated in a board by means of solder, the wave soldering operation station providing a wave of molten solder to the underside of the circuit board and the surface of the protruding leads. means for feeding the circuit board to the soldering operation station so that it can be deposited; and an excess desoldering operation station adjacent the wave soldering operation station, the excess desoldering operation station comprising: ( b) at least one hot air knife positioned below the transfer path of the circuit board and blowing a heated air jet directly onto the molten solder to be deposited on the bottom surface of the circuit board; (11) a pressurized air source; ) means for connecting said pressurized air source and said hot air knife; and (d) means for heating said heated air jet before blowing said heated air jet onto the underside of said circuit board, wherein said air jet an engraving of the auxiliary heat treatment specification (no change in content) for heating the said solder wave to a higher temperature than the solder wave; a hot air jet is impinged on the circuit board to which the still molten solder adheres, and the velocity of the hot air jet is high enough to remove substantially all bridges and strips, but at a moderate speed. Provided is a device characterized in that the wetting is insufficient to adversely affect the joint.

In the following discussion, the term "desoldering" refers to the actual displacing of solder from a circuit board and its interconnects, component leads, and/or component bodies; Refers to the repositioning of solder on the interconnects on the board, on the component leads and/or on the surface of the component body.

The following is an engraving of the margin WRa document (no changes to the content) The present invention is carried out by a mass soldering apparatus which essentially has a soldering operating station, in which the bottom of the board and the mutual soldering carried on the same board. A certain amount of molten solder is used to remove some of the solder adhering to the surfaces of the connectors, component leads and/or component bodies before cooling the solder to a temperature below the solidification temperature. can be mass welded to the bottom of the board. In accordance with the present invention, the circuit board can be passed horizontally through the crests of the standing wave of solder, and the airflow is directed to the circuit board substantially immediately after the circuit board and leads pass through the solder wave. ``directed so as to impinge on the underside and protruding leads of the

In the following detailed description of the invention, the term "component" refers to components without leads as well as components with conventional metal conductors or leads. The term "component lead" refers to the portion of a metallic conductor of any electrical or electronic component that is coupled to a printed wiring circuit board pattern, ie, a component lead, terminal, lug, via, etc. The term "land" as used herein refers to a metal groove or turn on a printed circuit board where a component or component lead is joined by solder. .

The term "fluid" is to be understood as referring to a gas or gas mixture. Air is usually used as the gas. If desired, the gas or gas mixture may contain liquid droplets dispersed within each. The term "mass soldering" as used herein refers to a technique in which liquid solder is applied to a circuit board from a puddle of liquid solder, such as wave soldering, contact or immersion soldering. , bot) (pot) soldering, jet soldering, cascade (casea'de)
Soldering may also be applied.

Next, a preferred embodiment of the present invention will be described in terms of a wave soldering system with reference to the accompanying drawings.

Referring first to FIG. 1, a printed circuit board 20 is loaded with a plurality of electrical or electronic components 24 at predetermined locations on the board at an insertion station 22. As shown in FIG. The board is a wiring board with one or more metal grooves printed on the underside of the board. Components 24 are mounted on the top side of the board, with their leads projecting downwardly through plate holes 25 that line up with the circuit lands to which they are to be bonded. These components may be inserted into this plate by any method known in the art, either single station or multiple station, well known in the art and requiring no further description. It may include either a manual assembly, which may have a centagraph or numerically controlled machine, or a semi-automatic or automatic assembly.

The next step is to treat the surfaces to be soldered with a so-called solvent in a solvent treatment operating station 30. The solvent may be any solvent well known in the art, and includes, for example, a mixed water/white rosin solvent, an activated rosin solvent, and a water-soluble solvent. The solvent may be applied by any method well known in the art, such as spraying, foaming, brushing.

The circuit board is then passed from the solvent treatment operating station 30 to the preheating operating station 32 where the board is preheated to render the solvent fluid and also removes most of the solvent.
to form an active solvent layer on the surface of the circuit board and lead wires. At the preheating operation station 32, either infrared or convection heaters, or a combination of infrared and convection side heaters, may be applied as is well known in the art. Preferably, but not necessarily, the preheating station 32 is expanded compared to conventional preheating stations and/or the preheating station 32 is heated to a temperature above the normal upper temperature of the circuit board 20. It is possible to raise the temperature from normal to high. Accordingly, circuit board 20 will be preheated to a minimum upper temperature of approximately 66°C. However, the plate will preferably be preheated to an upper temperature in the range of about 100°C to 125°C, or even higher. The purpose of preheating the board to a temperature higher than the normal top temperature is to increase the time that the solder remains molten on the surface of the board after it emerges from the solder wave. The reason for this will become clear from the following explanation.

The solvent treated and preheated circuit board is then passed to a mass wave soldering operation station 36. Referring also to FIGS. 2 and 3, the wave soldering operation station includes a heating device (not shown) throughout the container 40 for heating and maintaining the solder source 42 in a molten state. It may be attached to the bottom wall and/or side wall or dipped in solder.

The whole is shown at 44. A reservoir and nozzle assembly is located inside the container 40. Reservoir/nozzle assembly 4
4 may be of a conventionally known type, typically,
a rounded bottom wall 46; a pair of substantially vertically opposed end walls 48;
and 50, and a pair of sloped side walls 52 and 54. The upper ends of end walls 48 and 50 and side walls 52 and 54 define an elongated rectangular nozzle or slot 56 that projects a suitable distance, e.g., 1 inch, above the top surface of molten solder in container 40. are separated from each other.

Preferably, the reservoir directs the flow of solder overflowing from the nozzle 56, such as from a Kenneth G.? Inton (Kenneth G,
Boynton U.S. Patent No. 3,398,873
Reservoir side walls 52 and 5 can be controlled in accordance with the teachings of No.
A pair of adjustable partition plates 58A separated from 4.

It has 58B. The soldering operation station is equipped with a variable speed pump f (not shown) which communicates with an intake orifice 59 at the lower end of the sump and nozzle assembly 44 for pumping solder into the sump. The solder then accumulates in a pool and overflows from the nozzle 56 as a standing wave of solder.

An important feature and condition of the present invention is that the excess solder is relocated to the bottom of the circuit board and/or the excess solder is removed from the short pieces.
Interconnects carried from the bottom of the circuit board and onto the board before the solder solidifies as icicles and/or bridges;
It can be removed from all of the component leads and/or the component body. This is accomplished by processing the soldered circuit boards and dependent component leads at an over-soldering operation station 60. An excess solder removal operation station 60 immediately follows in alignment with the soldering operation station 36 and is adapted to reposition or blow away excess solder from the underside of the board before the solder solidifies as strips, icicles and/or bridges. It is designed to. The desoldering operation station 60 has one or more fluid jets, fluid knives, slots, nozzles or the like capable of directing a flow of fluid to the underside of the plate, each shown generally at 62. ing. If desired, a baffle plate 64 may be positioned below the passageway of circuit board 20 at an angle of about 45 degrees from the horizontal. This baffle 64 acts as a baffle for the fluid flow exiting the nozzle 62. Preferably, but not necessarily, the fluid is preheated to a temperature that will cause the plate to be modified/inserted. Fluid flow rate, fluid pressure, fluid temperature, and the time elapsed before the circuit board emerges from the solder wave and begins contact with the fluid stream are dependent on board temperature, ambient temperature, solder melting point,
the specific heat of the fluid, the heat transfer coefficient of the fluid to the base, the size and shape of the board, the component density, the amount of solder deposited and removed, the conveyor speed, and the It can vary over a wide range depending on distance. Preferably, the nozzle 62 is located close to the travel path of the plate. Of course nozzle 6゛2,
It shall be sufficiently spaced down from the travel path of the plate to allow clearance for the longest hanging leads, etc. Typically the impingement fluid is air, although an inert gas may be used as the fluid. The fluid is preheated to a temperature above the predetermined heating temperature of the solder in the solder wave, preferably within the range of about 290°C to 300°C (as measured at the exit of nozzle 62). For 63/37 solder alloy (melting point approximately 183°C), the preferred fluid preheat temperature is (nozzle 6
Measured at the exit of step 2) approx. 90°C to 300°C
14 (no change in content) ℃.

When a stream of air heated to a temperature higher than that of the molten solder is blown onto the underside of the circuit board, the excess solder forming the ridges, icicles, and strips is further heated and is very easily blown away.

Underside of circuit board, interconnects and component leads and (
or) Fluid flow impinging on molten solder stationary on the component body repositions excess solder on the underside of the plate, interconnects, leads and body; and/or)
Blows away excess solder from interconnects, leads, and the body, and minimizes the possibility of forming bridges, icicles, or slivers as the solder solidifies.

, FIG. 4 shows a preferred electrical and pneumatic control device according to the invention and is particularly suitable for using hot air as the fluid stream according to the invention.

Referring to FIG. 4, a nozzle 62 is connected to one side of a solenoid valve 68 via a supply line 66. The valve 68 is connected to a heater 7 adapted to heat the air to a desired high temperature.
The valve 68 is connected to the outlet of the printed circuit board 20 via a conduit 70 to the outlet of the printed circuit board 20.
through a suitable relay arrangement 76 so as to blow heated air through the solder wave and when the leading edge of the board intercepts the light beam emanating from a light source 78 located above the travel path of the board. connected. The flow of heated air allows the trailing edge of the printed circuit board to pass through the luminous flux emanating from the light [7B] and to re-reach the same luminous flux to the photovoltaic cell 74 until the valve 68 is closed or nearly closed. Continue. Preferably, all valves 68 are prevented from closing, i.e., at least a small amount of heated air flows through the nozzle so that the nozzle is maintained at the desired high temperature, thus eliminating heat lag. It is designed to make it possible.

A circuit board conveyor 80 of conventional construction is used in soldering systems. Conveyor 80 transports circuit boards from insertion operation stage 22 to solvent treatment operation station 30;
Wave Soldering Operation Station 36 and Excess Desoldering Operation Stage Specification; Preface (No Changes in Content) A pair of spaced conveyor rails 82 and 84 and suitable drive equipment (not shown) for passage to the sink 60. )have.

FIG. 5 shows the printed wiring circuit board 20 in the margin (FIG. 1) below the excess solder removal operation station 60 and how the thermal fluid flow in accordance with the present invention removes molten solder 86 from the circuit board 20, interconnects, and removal from the component lead wire 26.

One skilled in the art will be able to determine by experiment the preferred operating parameters to achieve mass soldering without spigots, bridges, and strips for the particular circuit board being soldered.

For example, a net circuit plan area of approximately 96.75 square centimeters, 150 0.0762 cm diameter plated through holes, and 150 0.0508 cm diameter component leads (50% with steel leads). wire, 50% copper lead wire), 63/37 solder alloy,
Solder bath temperature 252℃, preheating temperature approximately 125℃ (top side)
, has a conveyor speed of 0.018 meters per second, and (
At a pitot tube pressure of about 22.5 millimeters of mercury (measured at about 0.6 centimeters from the exit of nozzle 62) and a fluid velocity of about 76 meters per second (measured at the exit of nozzle 62). Hot air (290° C., measured at the exit of nozzle 62) is employed as the impinging fluid to eliminate solder wigs, bridges, and strips from a 6.35 x 15.24 cm circuit board. The distance between the point where the circuit board exits the circuit board and the point where the hot air flow begins passing through the board should be within the range of about 19 to 25 centimeters. Those who are familiar with this technical field should
It will be appreciated that the parameters are interrelated and can be varied in various ways to achieve the foregoing objectives of the invention.

Reference is now made to FIGS. 11-13, which illustrate a second form of mass wave soldering system according to the present invention. Wherever possible, the same reference numerals as in FIGS. 1 to 5 have been used to represent corresponding parts.

The mass wave soldering system shown in FIGS. 11-13 has many similarities to the mass wave soldering system shown in FIGS. 1-5. Thus, for example, a mass wave soldering system according to the invention includes a mounting operating station 22, a solvent treatment operating station 30, a preheating operating station 32, and a mass wave soldering operating station 36. However, in contrast to the systems of FIGS.
is passed substantially horizontally onto the crest of the solder wave.

Preferably, but not necessarily, a preheating operation station 32
be wider than conventional preheating operation stations;
and/or operating the preheat operating station 32 at a higher than normal temperature such that the plate 22 is heated to an upper temperature of 14 to 28° C. or higher than normal. Thus, for example, plate 22 may be preheated in accordance with the present invention to an upper minimum temperature of about 66°C, preferably an upper temperature within the range of about 79°C to 121°C. The purpose of preheating the board to a temperature higher than the normal upper temperature is to prolong the time during which the solder on the surface of the board remains molten after the board comes out of the solder wave.

As discussed with respect to FIGS. 1-5, the fluid flow is directed toward the bottom of the plate 20 substantially immediately after it emerges from the solder wave. This fluid stream impinges on the bottom of the plate 22 and repositions the solder on the bottom of the plate 22 and (or) the bottom of the plate and interconnects, component leads and structures carried thereon. Blow off excess solder from the element body, and in doing so reduce the possibility of formation of bridges or icicles or strips of solder once it solidifies, resulting in horizontal operation at a reduced peel-back angle. Keep it to a minimum regardless of the situation.

Otherwise, the operation and arrangement of the system of FIGS. 11-13 is the same as described above for the system shown in FIGS. 1-5.

Furthermore, the present invention has many advantages. - It has been found that, as an advantage, the contact of the underside of the circuit board with the fluid stream according to the invention results in uniform solder adhesion on the conductors of the same board.

Furthermore, stomas and unmounted plated through holes may be cleaned by the fluid stream. Another advantage is that the soldered plates can exit the system at a lower temperature compared to conventional mass soldering systems. This advantage primarily derives from the removal of excess solder, which is the primary heat sink in conventionally soldered boards. Furthermore, if the fluid stream is colder than the solder on the board, cooling can be made even faster. Cooling the board makes it easier to handle the board after soldering.
As a result, the solder cut solder system (solder cut solder system)
er-cut-soldersystern) to-p'
? The accompanying y-drift (pad 1ift) can also be suppressed to a small extent. If the board is cooled, even finer particles will be soldered.

The embodiments of the invention described above may be varied in various ways without departing from the inventive features described herein. For example, single layer or multiple heaters similar in construction to a preheater may be incorporated into the over-soldering operation station 60 to increase the time that the solder remains molten on the surface of the board. Furthermore, a small amount of liquid droplets, e.g. up to 20% by weight, may be added to the fluid, e.g.
It may be dispersed into the gas stream by one or more aspirator nozzles 98. Aspirator nozzle 98 is a source 10 of liquid to be dispersed into the gas stream.
2 by a conduit device 100. Obviously, liquid droplets can be injected into the gas stream using one or more atomizing nozzles. The liquid must be of a material compatible with soldering operations. - For example, the liquid can be a conventional soldering oil or a mixed oil. The liquid droplets may have the effect of increasing the fluid flow mass of the gas stream and thus increasing the rate of solder removal from the board and leads. Additionally, employing the soldering oil as a liquid may facilitate post-soldering cleanup and may produce shinier solder joints. Conventional wetting agents and/or flow agents may also be dispersed into the fluid stream if desired. And also one or more auxiliary heaters may supplement heater 72 and/or replace heater 72, e.g.
As shown in Figures 10 and 10, such integrated heaters may be electrical resistance heaters or may be cartridge heaters.

Particularly referring to FIGS. 7 and 8, the heater and nozzle combination shown in these figures is in the form of a flat elongated trapezoidal cavity and is generally shown at 104. An intake orifice 10G is formed in the short side wall 108 of the manifold 104 and the conduit device 1 (not shown)
is connected to a source of pressurized air (not shown). One of the long walls 110 of the manifold 104 is tapered to form an elongated knife-shaped orifice 112. Orifice 112 defines a nozzle outlet for directing fluid flow to a circuit board in accordance with the present invention. Manifold 104 is formed from a heat resistant material such as welded steel plate. Mounted within the manifold l' I Q 4 is a heating device, such as one or more electrical resistance heating elements 11.1. Electrical resistance heating elements 114 are known in the art and commercially available. If desired, the walls of the manifold may be thermally insulated in known manner. 61U body 3iE rl when activated.

It is heated by flowing over the resistance heating element 114.

Another preferred embodiment of the heater/nozzle combination is shown in FIGS. 9 and 10. In this illustrated preferred embodiment,
The nozzle is a generally rectangular block 116. Block 116 is made of a heat resistant material such as steel. A plurality of blind holes 118 are formed in one sidewall 120 of block 116 and accommodate an equal number of cartridge heaters 122. Cartridge heaters are well known in the art and commercially available. A hollow chamber 124 is formed inside the block 116 and an inlet orifice 125 is formed inside the block 11.
6, connecting the hollow chamber 124 to a source of pressurized air (not shown) by a conduit arrangement (not shown).

A nozzle exit orifice is formed in a side wall 126 opposite the wall 120 on which the cartridge heater 122 is mounted. As seen in FIG.
32 and is tapered to form an intersection with 32. Passage 132 communicates with hollow chamber 124 . The edge surfaces 128 should be substantially coplanar with each other and may be substantially knife-edge as shown or along a plane as shown by dotted line 134 at the end of the nozzle exit. It may have a more substantial width, such as being made by cutting. An interesting feature and advantage, namely cutting the nozzle outlet to give it a substantial width, is that the working gas flow exiting the nozzle turns out to be particularly smooth. It has also been observed that using this type of nozzle outlet, secondary air flows are created on each side of the working gas flow. These secondary air flows become fluid insulation sheets for the working gas flow,
It can also directly assist in repositioning or removing solder.

Although the desoldering operation station according to the present invention is illustrated in combination with a mass wave soldering system, those skilled in the art will appreciate that similar advantages exist for the desoldering operation station in combination with immersion, gasket, jet and drag soldering systems. It will be appreciated that this may be accomplished by employing it in combination with other types of mass soldering systems, such as.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the mass soldering system according to the present invention, FIG. 2 is a partially sectional side view of the soldering device portion of the soldering system shown in FIG. 1, and FIG. 3 is a partial cross-sectional side view of the soldering device portion of the soldering system shown in FIG. 4 is a schematic diagram of an electropneumatic control device of the same device, and FIG. 5 shows a circuit board at an intermediate step in the process of the invention, and in which excess solder is removed in accordance with the invention. FIG. 6 is a view similar to FIG. 5 showing an alternative soldering device according to the invention, and FIGS. 7 and 8 are respectively in accordance with the invention. FIG. 9 is a plan view and cross-sectional view of one form of a fluid flow nozzle structure useful in the soldering apparatus of the present invention; FIG. 10 is a vertical sectional view of the nozzle structure of FIG. 9, FIG. 11 is a side view of the second soldering device embodying the present invention as seen along the travel path of the circuit board, and FIG. 12 is a partially sectional side view of a part of the wave soldering device of the soldering system of FIG. 11, and FIG. 13 is a plan view of the wave soldering device portion of FIG. 12. 20... Printed wiring circuit board, 24... A plurality of electrical or electronic components, 25... A plurality of holes, 26... Lead wires, 36... Mass soldering operation station, 4
0... Supply source of molten solder, 6o... Excess solder removal operation station, 62... Air knife projector, 8
0... Circuit board transfer means (conveyor), 86... Molten solder F/, 1. Engraving of drawings (no change in content) F/θ, 2. Engraving of drawings (no change in content)

Claims (1)

[Claims] 1. An apparatus for mass-bonding electric and electronic components incorporated in a circuit board by soldering, the apparatus having a lead wire projecting downward through a hole in the circuit board. , a wave soldering operation station that provides waves of molten solder;
means for feeding the circuit board to the soldering operation station so as to deposit molten solder on the underside of the circuit board and on the surfaces of the protruding leads; and excess solder adjacent to the wave soldering operation station. a removal operation station, the excess solder removal operation station comprising: (a) blowing a heated air jet directly onto the molten solder located below the transfer path of the circuit board and deposited on the lower surface of the circuit board; (b) a source of pressurized air; (c) means for connecting the source of pressurized air and the thermal air knife; and (d) before blowing the heated air jet onto the underside of the circuit board. The apparatus having means for heating the jet, comprising auxiliary heating means for heating the air jet to a temperature higher than the solder in the solder wave, the air knife being directed at the solder wave, A hot air jet is impinged on the circuit board to which the molten solder has just passed the wave, and the velocity of the hot air jet is such that it removes substantially all bridges and strips. device characterized in that it is large enough, but not large enough to adversely affect joints that can be moderately wetted. 2. Apparatus according to claim 1, comprising means for introducing liquid droplets into the heated air. 3. Apparatus according to claim 1, comprising a source of liquid droplets, and wherein the means for introducing liquid droplets includes at least one aspirator connected to the source. 4. Apparatus according to claim 2, comprising a source of liquid droplets, and said means for introducing liquid droplets having at least one atomizing nozzle connected to said source. 5. The hot air knife includes (a) valve means for creating a continuous small air flow in the air knife; and (b) sensing the presence of the circuit board on the solder wave.
Claims 1 to 4 further comprising detection means for opening the valve means and directing a complete air jet onto the circuit board as soon as the circuit board leaves the solder wave. equipment. 6. The apparatus according to any one of claims 2 to 5, wherein the auxiliary heating means is comprised of one or more integrated heaters integrated with a hot air knife. 7. The device of claim 6, wherein the integrated heater is an electric resistance heater. 8. The device according to claim 6, wherein the integrated heater is a cartridge heater.